Ask an attacker to sketch their ideal target. Identities mid-migration. Overloaded and reorganized IT teams. Blurred responsibilities between seller and buyer. Temporary interconnections built in a hurry. And a public announcement documenting it all in the press. That is the exact portrait of an M&A deal in progress. Here is why cyber resilience M&A must be a program workstream, not an afterthought.
Why is the M&A window so exposed?
Three factors compound. First, the attack surface. During the transition, two IT landscapes coexist, linked by temporary bridges. Indeed, every TSA interconnection is a door between two companies. Second, disorganization. Security owners change, vigilance processes slacken, weak signals go unnoticed. Third, social engineering. The deal announcement hands attackers a ready-made phishing scenario, such as a new login procedure following the merger. Yet disoriented employees are more vulnerable to it than ever.
Inheriting liabilities: the buyer’s risk
Acquiring a company means acquiring its security posture: vulnerabilities, dormant compromises, non-compliances. Indeed, several major incidents of recent years came in through a freshly acquired subsidiary, connected before it had been audited. The rule is simple: no interconnection without a prior audit of the acquired environment. You also remediate critical gaps before you open the flows. Ideally, this work starts before signing, during IT and cyber due diligence.
Cyber resilience M&A: surviving, not just protecting
The question is not only preventing the attack. You also have to survive it mid-program. What happens to a continuity plan inherited from the seller’s group when the entity becomes autonomous? Who activates the crisis cell during the transition, the seller or the buyer? Thus, the business continuity and crisis management capability must be redefined for the new entity. Moreover, it must be tested before Day 1. Finally, it anchors to the applicable obligations (NIS2, DORA), which apply with no grace period.
Cyber resilience M&A: the takeaway
In an M&A deal, cyber resilience M&A is not an insurance policy you take out after moving in. It is a component of the separation or integration plan, with its milestones, its budget and its owner. The attackers know your calendar. Make it work for you instead.